Detection of a latent fingerprint is an important means for criminal investigation, which will be evidence necessary for identification, arrest and charge of criminals. In most cases, the detection of fingerprint is conducted by the following method. A surface of a specimen to which fingerprint is attached or suspected to be attached is swept softly with a brush containing aluminum powder so that the aluminum powder sticks to the fingerprint, and then the powder is copied onto gelatin paper. However, when the specimen is a specific material including a metallic deadly weapon such as a handgun and a knife, a synthetic leather, and an adhesive face of an adhesive tape, the above method cannot copy the fingerprint clearly. Instead of the above method, a method in which 2-cyanoacrylate is vaporized and converted to white polymers with moisture on a fingerprint so as to detect the fingerprint has been used as a method for developing a fingerprint residue more clearly.
The detection of fingerprint using 2-cyanoacrylate is usually carried out by means of allowing a vapor of 2-cyanoacrylate (monomer) to adhere to a fingerprint, and there have been various reports on details thereof, including a method in which a gel formulation is used as disclosed in Patent Document 1, a method in which 2-cyanoacrylate (monomer) is dropped to powder so as to volatize as disclosed in Patent Document 2, a method in which 2-cyanoacrylate (monomer) is sprayed as disclosed in Patent Document 3, a method in which 2-cyanoacrylate (monomer) is impregnated into woven or non-woven fabric as disclosed in Patent Document 4, and so on.
However, since 2-cyanoacrylate polymer attached to fingerprint is white, it can hardly detect the fingerprint on whitish specimens such as shopping bags and aluminum foils, and is disadvantageous in that it requires an advanced technique for taking a picture such as photographing with oblique rays.
To address the above problems, detection with high sensitivity has been made possible by allowing a fingerprint ridge obtained from 2-cyanoacrylate polymer to contain a fluorescent colorant so as to emit fluorescence in accordance with a method in which a mixture of 2-cyanoacrylate and a fluorescent colorant is sprayed as disclosed in Patent Document 5, a method in which 2-cyanoacrylate is allowed to adhere to a fingerprint, and then soaked in a solution of a fluorescent colorant so as to be developed for detection as disclosed in Patent Document 6, and the like.
However, these wet methods using organic solvents cannot avoid deterioration of specimens by the organic solvents when specimens made of plastics or the like are used. Also, organic solvents are problematic in terms of flammability and toxicity.
To address the above problem, a method has been reported, which is a dry method in which vapors of 2-cyanoacrylate (monomer) and a sublimation dye are simultaneously used as disclosed in Patent Document 7.
However, when a fluorescent colorant is used in combination with 2-cyanoacrylate as in Patent Documents 5 and 7, a basic fluorescent colorant cannot be used due to solidification of 2-cyanoacrylate, and thus a disadvantage arises in that kinds of fluorescent colorants which can stably be used are largely limited. In addition, it is not preferable that 2-cyanoacrylate is used in combination with fluorescent colorants from the viewpoints of storage stability and handling at the scene.
Moreover, all the above-described methods for detecting a fingerprint using 2-cyanoacrylate have a problem such that 2-cyanoacrylate polymer is difficult to be wiped from the specimen in order to restore it after fingerprint has been detected, and thus inferior in restorability.    Patent Document 1: JP-A-S60-502088    Patent Document 2: JP-A-S60-222033    Patent Document 3: JP-A-S61-288836    Patent Document 4: JP-A-S62-47343    Patent Document 5: JP-A-S63-161939    Patent Document 6: JP-A-H02-268744    Patent Document 7: JP-A-H11-9575